XP and You have just ignored an incoming call message

OK I gave into the devil and install XP Home edition on my machine. Now generally I like it but since I have installed it when I am online I often get an alert pop-up saying "you have just ignored an incoming call" - now I know I haven't been ignoring phone calls so what else can this message mean and how do I stop it popping up?? It's driving me nuts.

Pounding at a thick stone wall won't move it, sometimes, you need to step back to see the way around.